For example, in a rolling mill, upper and lower work rolls are rotated by upper and lower drive shafts via gear spindles (a type of a gear-type universal joint) slanted vertically by a slant angle θ (θ=0 to 3 degrees), so that the rolling mill rolls a strip.
A conventional gear spindle of this type is shown in FIG. 6 as an example (see Patent Document 1).
In this gear spindle in FIG. 6, reference numerals 100 and 101 respectively denote a spindle inner cylinder and a spindle outer cylinder, and the shaft axis of the spindle inner cylinder 100 is slanted by a slant angle θ relative to the shaft axis of the spindle outer cylinder 101. Reference numeral 102 in FIG. 6 is a hub, and a gear portion (external teeth) 102a is provided on an outer periphery of the hub 102. A communication hole 102b is formed, penetrating the gear portion 102a. The hub 102 is fitted around an end portion of the spindle inner cylinder 100 such that the hub 102 is allowed to slide axially by a spline 103.
An end portion of the spindle outer cylinder 101 on the rolling mill side is detachably fitted around an oval portion 104a of a work roll 104, and an annular Y-seal 105 is attached to an end portion of the spindle outer cylinder 101 on the driving device side via a seal case 106 such that the Y-seal 105 is movable radially. A gear portion 101a provided on an inner periphery of the spindle outer cylinder 101 meshes with the gear portion 102a of the hub 102 in such a manner as to be slidable axially. An oil-supply-side oil chamber 107 and a seal-side oil chamber 108 are formed with the meshing portion between the gear portions 101a, 102a being the border therebetween. A lubricant 110 is supplied into the oil-supply-side oil chamber 107 through an oil supply hole 109 formed in the inner periphery of the spindle outer cylinder 101. In FIG. 6, reference numeral 111 denotes a boot-shaped seal, 112 denotes an inner-cylinder pivot (thrust pin), 113 denotes a helical compression spring, and 114 denotes a stopper.
According to the above configuration, a rotary torque of a drive shaft is transmitted from the spindle inner cylinder 100 slanted at the slant angle θ, to the hub 102 via the spline 103, and therefrom, transmitted to the spindle outer cylinder 101 via the gear portions 101a, 102a at same velocity. The work roll 104 is thereby rotated. Meanwhile, the gear portions 101a, 102a are lubricated over their entire peripheries with the lubricant 110 so that they may undergo less wear and generate less heat.